Do cluster roots of Hakea actities (Proteaceae) acquire complex organic nitrogen?

Schmidt, S., Mason, M., Sangtiean, T. and Stewart, G. R. (2003) Do cluster roots of Hakea actities (Proteaceae) acquire complex organic nitrogen?. Plant and Soil, 248 1-2: 157-165. doi:10.1023/A:1022352415728

Author Schmidt, S.
Mason, M.
Sangtiean, T.
Stewart, G. R.
Title Do cluster roots of Hakea actities (Proteaceae) acquire complex organic nitrogen?
Formatted title
Do cluster roots of Hakea actities (Proteaceae) acquire complex organic nitrogen?
Journal name Plant and Soil   Check publisher's open access policy
ISSN 0032-079X
Publication date 2003
Sub-type Article (original research)
DOI 10.1023/A:1022352415728
Volume 248
Issue 1-2
Start page 157
End page 165
Total pages 9
Place of publication Dordrecht, Netherlands
Publisher Kluwer Academic Publishers
Collection year 2003
Language eng
Subject C1
270402 Plant Physiology
270201 Gene Expression
620501 Field crops
620502 Horticultural crops
Formatted abstract
Although there has been speculation that cluster roots play a role in plant nitrogen (N) acquisition there have been few experimental studies, demonstrating this. We grew the subtropical wet heathland plant Hakea actities in sand and in axenic vermiculite-sand cultures to investigate its use of different N sources. Seedlings produced greater quantities of cluster roots when grown with NO3, glutathione or protein as N sources than with NH4 +, glutamine or without N addition, suggesting that N source influences cluster root initiation and development. Axenically grown seedlings acquired more N when grown with 4.5 mM than with 0.5 mM glutathione or protein as N sources suggesting that seedlings are able to assimilate complex organic N. However, control seedlings that did not receive N other than seed storage N (approximately 0.2 mg N) acquired 2 mg N from an unknown source, so that data are not unequivocal. Peptidase activity in extracts derived from non-axenic cluster root tissue changed with age of cluster roots. Developing and mature cluster roots had higher peptidase activity than young and senescing cluster roots. To determine whether peptidases are associated with the outer surface of cluster roots, entire cluster roots were gently centrifuged and the resulting solution analysed for peptidase activity using gelatine-containing PAGE. Different peptidases were active at different times of cluster root development, suggesting that plant or microbially derived peptidases could play a role in organic N acquisition by cluster roots. Roots and cluster roots expressed a putative amino acid transporter (HaAAT4-1) and peptide transporter (HaPepT1) as determined by northern blot analysis. Expression of HaPepT1 in cluster roots increased throughout cluster root development although further studies need to confirm this.
Keyword Agronomy
Plant Sciences
Agriculture, Soil Science
Amino Acid Transporter
Cluster Roots
Organic Nitrogen
Peptide Transporter
Amino-acid Transporters
Proteoid Roots
Q-Index Code C1

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Created: Tue, 14 Aug 2007, 19:06:04 EST